What does no MX record found mean for email delivery?

It means sending mail servers can't find where to deliver your mail. Without an MX record pointing to a mail host, inbound email bounces with a 550 error.

Why doesn't my domain have an MX record?

Common causes include: no MX record published at all, the MX target not resolving to an A/AAAA record, or an MX pointing to a CNAME (which is illegal per RFC standards).

How do I fix missing MX records for my domain?

Publish an MX record pointing at your mail provider's hostnames (e.g., aspmx.l.google.com for Google Workspace). Verify the target resolves, then wait for the old record's TTL to expire.

What's a null MX record and when should I use it?

A null MX is a record with priority 0 and target '.' (bare dot) that explicitly tells senders your domain accepts no mail. Use it for parked or send-only domains instead of leaving MX blank.

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No MX record found: why inbound email bounces

2026-06-21 · mx · dns · email · deliverability · bounces

mxdnsemaildeliverabilitybounces

"No MX record found" means a sending mail server queried DNS for your domain's mail-exchanger records and got nothing back, so it has no idea which host to deliver mail to. The result is bounced inbound email — senders get a 550 or a delayed-delivery report instead of reaching your inbox. The fix is almost always to publish a valid MX record pointing at a mail host that actually resolves, then wait out the TTL.

What an MX record is

An MX record is a DNS record at your domain's apex (or a subdomain) that names the host responsible for receiving mail, plus a priority. A working set looks like this:

dig +short MX example.com
1 aspmx.l.google.com.
5 alt1.aspmx.l.google.com.
10 alt2.aspmx.l.google.com.

Lower priority numbers win; senders try the lowest first and fall back to higher ones. The hostname on the right (the MX target) must resolve to an A or AAAA record — that is where the SMTP connection actually goes.

Why you see "no MX record found"

A handful of root causes, in rough order of frequency:

No MX record is published. The domain has A/TXT records but nothing of type MX. Common on domains set up for a website but never configured for mail.
The MX target does not resolve. You published 1 mail.example.com. but mail.example.com has no A/AAAA record, so the connection has nowhere to land.
Only an A record exists. Per RFC 5321, a sender may fall back to the domain's A record when no MX exists (the "implicit MX" rule). Many do not — never rely on it, publish an explicit MX.
Recent change still propagating. The old (empty) answer is still cached for the length of its TTL.
The MX points at a CNAME — illegal. RFC 2181 and RFC 5321 forbid an MX target from being a CNAME. It must name a host with A/AAAA records directly. Some resolvers reject it; others behave unpredictably.

How to fix it

Publish an MX record pointing at your mail provider's hostnames. For Google Workspace that is aspmx.l.google.com (priority 1) plus the alternates; for Microsoft 365 it is <tenant>.mail.protection.outlook.com (priority 0). Then confirm the target resolves:

dig +short A aspmx.l.google.com

If that returns addresses, mail has somewhere to go. After publishing, mail keeps bouncing only until the previous record's TTL expires — set a low TTL before a planned cutover so you are not stuck for hours.

The null MX (deliberate "no mail")

If your domain genuinely never receives mail, do not just leave MX blank — declare it. RFC 7505 defines the null MX: a single record with priority 0 and a target of . (a bare dot).

example.com.  IN  MX  0 .

This tells senders explicitly that the domain accepts no mail, so they bounce immediately instead of timing out or falling back to your A record. It is the correct posture for a parked or send-only domain.

Run the MX check on your domain →

Frequently asked questions

What does no MX record found mean for email delivery?: It means sending mail servers can't find where to deliver your mail. Without an MX record pointing to a mail host, inbound email bounces with a 550 error.
Why doesn't my domain have an MX record?: Common causes include: no MX record published at all, the MX target not resolving to an A/AAAA record, or an MX pointing to a CNAME (which is illegal per RFC standards).
How do I fix missing MX records for my domain?: Publish an MX record pointing at your mail provider's hostnames (e.g., aspmx.l.google.com for Google Workspace). Verify the target resolves, then wait for the old record's TTL to expire.
What's a null MX record and when should I use it?: A null MX is a record with priority 0 and target '.' (bare dot) that explicitly tells senders your domain accepts no mail. Use it for parked or send-only domains instead of leaving MX blank.